The Scoop on Chicken Poop

Turn that manure into compost instead of applying it to fields

By Dr. Francis Gouin

The new governor of Maryland has made a major error in allowing poultry farmers to continue applying their phosphorus-laden chicken manure on land that is already overloaded with phosphorus.
What the chicken farmers and the governor are ignoring is scientific evidence that clearly identifies excessive levels of phosphorus in soils as the cause for phosphorus-induced trace element deficiencies, lower yields, lower nutrient values and Bay pollution.
The smarter strategy is to grow soybeans one year then corn the next. Legumes like soybeans fix their own nitrogen and leave plenty in the ground to grow a crop of corn the following year. If this rotation were followed, farmers would only need to apply potassium when soil call for it. When the soil needs potassium, it can be added as either potassium chloride or potassium sulfate, both cheaper to apply than tons of chicken manure.
Phosphorus is essential to plant growth. But too much causes other essential plant nutrients to bind to it, starving plant roots. Such essential trace elements as iron, zinc and copper are essential to plant growth, as are nitrogen, phosphorus, potassium, calcium and magnesium. In the mid 1970s I was asked by fellow University of Maryland faculty members who specialized in vegetable crops to review soil tests from fields of sweet potatoes near Salisbury. The total phosphorus levels in those soils were so high that they were reducing yields. I recommended they stop applying phosphorus and apply only nitrogen. This was a major change in culture for these farmers because they had been accustomed to applying tons of 10-10-10 before planting each season’s crop.
So much phosphorus had been applied that it took several years with none before yields started to increase.
In the early 1980s, rhododendron growers tried dosing their plants with lots of phosphorus to force them into flower under shade. It worked, but it also stunted growth and caused iron deficiency symptoms on the foliage. Full sun alone would have produced healthy tall plants with flowers.
My conclusion from these and other studies is that plants do not need much phosphorus to be productive.
Over-applying phosphorus not only leads to reduced yields and lower nutritional value. It also contributes to Bay pollution.
Allowing farmers to make yearly applications of chicken manure on soils already saturated with phosphorus lowers yields of grain and forage crops. Since most of these farmers do not plant cover crops, their phosphorus-enriched soils erode into the Bay.
There are other better uses for chicken manure, as compost or as a source of energy. The ornamental horticulture industry — the second largest agricultural industry in Maryland and the nation — is a ready market for quality compost. Yet Maryland has to import compost from as far as Maine to meet its needs. Maryland Environmental Services is well versed in the science and technology of making compost.
Gov. Hogan, please encourage chicken farmers to form a co-op to manufacture and market compost.